Process of manufacturing cement



Jan. 15, 1929. 1,699,451

T. RIGBY PROCESS OF MANUFACTURING CEMENT Filled July 20, 1925 2SheetS-Sheel 1 Jan. 15, 1929.

T. RIGBY PROCESS OF MANUFACTURING CEMENT Filed July 20., 1925 12ASheets-Sheetl 2 P"Patented Jan. 15, 19.29.

UNITED STAT-Es THOMAS RIGBY, OF LONDON, ENGLAND.

PROCESS OF MANUFACTURING CEMENT.

Application filed July 20, 1925, Serial No. 44,865, andin- Great BritainJuly 28, 1924.

Thisinvention is concerned with cement making by the Wet method inrotary kllns by atomizing or similarly dispersing the c ement slurry ina finely divided cond1t1on 1n the gases in the kiln so that these lattershall exert a drying action upon and be somewhat cooled by the slurrybefore it is collected on the internal wall of the kiln and it is to aprocess involving this that ,reference is made hereinafter and in the.appended claims by the expression a cement making process of the kindreferred to.

It is the practice at the present day to allow the slurry to pour in aliquid stream into the upper end of the kiln and as far as I am aware nocement making process of the kind referred to is in use. I have-observedthat itis of considerable importance to the practicability of such aprocess to secure a comparatively extended zone of contact along thekiln from its mouth inwards between the gases and' the dispersed slurryand further that it is important to arrange for the dispersal of theslurry in correct quantities along such an extended zone of contact insuch a manner that the quantity being dried at any part of the extendedzone is in proportion to the temperature differences available at suchpart between the outgoing kiln gases and the disn persed material and sothat the water content of the partly dried material collected on thekiln walls is of the desired percentage at th at part owing to suchcorrect proportioning.

I secure according to one feature of the invention extended Contact asaforesaid by introducing the slurry into the kiln by a plurality ofspraying nozzles or the like respectively delivering the atomized orsimilarly di spcrsed slurry into the gases at different regionslengthwise of the kiln. Such devices may be arranged inside the kiln atdifferent points along it or one or more of them may be outside the kilnbut preferably all are outside the kiln and respectively operate toproject the slurry to different distances in it.

While it is preferable as indicated to secure an extended zone ofcontact in the kiln between the atomized or similarly dispersed slurryand the gases, it is usually undesirable that these conditions should besecured in any way which admits of the dispersed material remainingsuspended in the gases by reason of the rate of flow' of the latter andconse quently I prefer that the material though dispersed in anapproximately finely, divided condition should be impelled through thegases in a direction and with a sufficient mo,- mentum to ensure thesame being collected Where desired' on the internal wall of the kiln.Ordinarily it will still bemoist enough then to have a suflicienttendency to cling to the kiln wall or to other particles of driedmaterial, a tendency which it retains at a moisture content ofsubstantially less than the moisture which the slurry will usually havewhen after the dispersal 1t reaches the kiln wall. Having once adheredto the kiln Wall the likelihood of the gases sweeping this material toany undesired extent along and from the kiln can practically be ignored.As the de posited material dries on the kiln wall it coheresadvantageously from the latter point of view while any excessivetendency for it to build up on the kiln wall may be overcome readily bythe provision of scraping devices in the kiln such for instance as loosechains or a loose bar or a fixed bar lying along the bottom of theinside of the kiln.

`Unless as is done in accordance with another feature of my inventionarrangements are made to guard against it, a likely cause c of troublein the Working of a cement making process of the kind referred to is thedifficulty of keeping a spraying nozzle or the like that is in a kiln inregular operation and in avoiding interrupting the operation of a kilnto attend to such a device when attention to it is requisite.Suchidificulties may in the absence of measures such as I shall refer toarise from the heat to which such a device becomes exposed or thetendency for slurry to become deposited on the outside of it and of aconduit that leads to it and while these troubles may be overcome bycareful provision for water or air cooling these parts or by disposingthem in the vupper portion of the inside of the kiln and providing fortheir ready Withdrawal from the kiln for attention without interruptingthe working of the kiln I provide, according to this other feature ofthe invention which I have just referred to, for placing a slurrydispersing device not only outside the kiln but actually outside the gaspassage of the kiln head so that the device operates in a cool placewhere it can be under constant observation and can be easily kept cleanand' adjusted at all times and from which place it projects thedispersed slurry into the kiln head through the gas space in the latterand thence into the kiln.

- Another feature of the invention and thatr aims at providing foruninterrupted cement manufacture in a lant where slurry is atomized orsimilarly dispersed in the k1ln and in spite of such interruptionsin-atomization as may be inevitable, is the provision of alternativeslurry feed means for the kiln of which one is the atomizing or likemeans and the other is means for directing into the kiln slurry in aliquid stream (or compact fluid mass) as or much as is the customarypractice, the latter means being organized so that it does notconstitute any interference to the proper conduct of the atomization inthe normal working of the kiln with slurry fed in this latter way.

Another of the features of the invention is the utilization to cool orcleanse the gases from the kiln, of slurry that is on its way to theatomizing or like device of the kiln and which slurry-f thereforebecomes in consequence enriched in cement materials either by itscleansing action or by evaporation of Water from it by the heat of thegases and doubtless in ractically all cases from both causes. to notethat ll have observed that usually slurry is supplied to rotary kilns ata water content (say some 40%) substantially higher than. it would needto have (say some 36-37 to render it fluid enough for pumping or foratomization in any customary manner. This is probably the result of aminimum limit kof water contentv determined as necessary for effectivelygrinding the solid materials of the slurry in the wet condition andenable such enrichmentof a slurry of normal water content as I havereferred to to be carried to a substantial extent without detriment tothe convenience withwhich it can be pumped o atomized.

The above and other objects and features of the invention will becomefully evident to those skilled in the art from the following descriptionwith reference to the accompanying drawings of certain forms ofcementmaking plant and'method illustrative of the invention.

ln the accompanying drawings: y Figure 1 shows in sectional sideelevation the general arrangement of one form ot installation -accordingto the invention;

Figure 2 is a sectional plan of part of the installation shown in Figure1;

Figure 3 shows in sectional side elevation, i

but to an enlarged scale, part of the installation shown in Figure 1;and

Figure 4 shows in sectional side elevation the lower portion of the kilnhead and illusy trates how, if desired, this portion of said head may beutilized as a reservoir for liquid-for instance slurry-serving as acooler and washer for the gases issuing trom the kiln.

lin Figures 1 and 2 the upper end oit the kiln is shown at 3 openinginto the kiln head through the rear wall 5 of which (see also In t isconnection it is important Figure 3) three slurry spraying nozzles 6, 7and 8 are shown as operatlng. 'llhjese project the spray into the kiln(through the gas space ot' the kiln head) to different distances, thespray from the nozzle 6 being shown diagrannnatically as opening out tothe internal kiln diameter at about'a, a', that from the nozzle 7 atabout I), b, and that from the nozzle 8 at about c, c. The nozzles are.set at a slight angle to one another so as to converge and to compensatefor the fact that none of them is axial with thekiln and the sprays fromthem interpenetrate to a certain extent, that which reaches to c, cpassing for instance through the two others. The sprays enter the gasspace 9 through circular openings (see 11 Figure 3) in the end Wall of achamber 13 adjustable axially of the kiln in an opening 15 (Figure 2) inthe wall 5. Each nozzle is secured upon a carriage 17 by adjustment otwhich (by rotation of a screw v19) the nozzle may be adjusted axiallyrelatively to a tubular hood 21 (in which the screw is lheld againstaxial movement) and l through an opening 23 in the end wall of which thespray from the nozzle passes to the opening in the end wall of thechamber 13. Openings (not shown) are provided in the lowest portion ofthe hood throu h which slurry collecting in the hood may rain out into adischarge trough 25. The hood is held adjustably in position in thechamber 13 by three or more clamping screws extending against itradially from a ring 27 secured to the chamber and this arrangementenables the hood and jet to be adjusted readily to any desired anglewith the axis of the kiln for the correct projection o f the spray toits zone in the kiln. A stud 29 may project from the end wall of thehood to assist, by contact with the end wall of the chamber 13, inlocating the hood axially. Thetubular hood 21 with its opening 23relatively to which the nozzle is adjustable is an example ot meanswhich may be conveniently used to control thfe amount of atomizedmaterial1 entering the kiln by using an apertured plate or battle in thepath of the spray to control the proportion of the spray issuing fromthe nozzle which it is desired shall be admitted to the kiln. Anyportion of the spray which strikes the baflie will not pass into thekiln but will coalesce and become slurry again which flows away from thekiln by the troughs 25.

The provision of a chamber such as 13 with an opening such as 11 throughwhich the spray of slurry passes into the kiln head and through the gasspace thereof to enter the kiln atords a convenient means whereby tobring a slurry spray nozzle or similarly atomizing or dispersing deviceas close as possible to the kiln mouth while yet guarding the deviceitrom exposure to the gases and the heat thereof and making it readilyaccessible for f being as :tar as possible maintained at allA till -fromthe the proper head prevails.

attentionso that the device remains free lfrom caked slurry or depositson it of material ases and is at all times cool and easily han led at amoments notice. Such an arrangement is to be regarded however merely asillustrative of one of` many ways in which a similar result may besecured since, for example, to secure in a cement making process of thekind referred to that a device that projects slurry in an atomized orsimilarly dispersed condition into a rotary kiln shall be guarded fromthe gases and the heat' thereof and be at all times convenient forattention to, it no more need be necessary the kiln head more or less inline with the kiln mouth and outside which the device operates toproject the slurry through that opening and so into the kiln.

rlhe slurry is preferably fed to the nozzles by an arrangement that,ensures the requisite ditlerences of pressure or head at the nozzlestimes during the working. This is best achieved in a simple way if asingle slurry pressure feed system be used for all the nozzles and thevarious nozzles fed by tapping for each one that system at a point in itwhere Thus for example a slurry force pump may feed the slurry along aconduit to an exit and the conduit be divided between the pump and exitby suitable constrictions into sections in which prevail pressuresdiering by say a pressure of some 20 lbs. per square inch so that forexample one nozzle may be connected to a section at a-pressure of' some7() lbs. another nozzle to one at a pressure of some 50 lbs. and so on.Alternatively a slurry pump may raise the slurry to an open tank at agiven height above the kiln and from which slurry may iow both to one ofthe nozzles and to another open tank at a lesser height above the kilnfrom which latter tank slurry may flow both to the second nozzle and toyet another tank still above the kiln level and so on.

Apparently any readiness of kiln gases to carry atomized material insuspension falls o with increasing wetness of this material.Consequently it in atomizing slurry in the kiln in zones along the kilnin a manner as indicated, the nearer the kiln mouth any particular zoneis the greater is the quantity of slurry atomized in that zone inrelation to the drying capacity of the gas current in that zone onmaterial atomized in it, a condition can be created that has as one ofits advantages a tendency to minimize the carrying or dispersed-materialout of the kiln by the gases. rllhis is becauseI under such conditionsthe zones are progressivel wetter in the direction of the kiln mouth sot at that material which has to be transported the lesser distance bythe gases to carry it out of the kiln is the less easily carried by thegases. In determining the water content 'of the slurry collected on thekiln in different zones that shall be accepted as leading to anypredetermined average water content of the whole of the slurry passmdown the kiln out of the zone furthest from t e kiln mouth, allowancemay have to be made for the d ing of the slurry -which occurs after itis co lected on the kiln wall until it leaves the last mentioned zonethis bemg an exposure to drying action thatevidentl varies with thedistance from the kiln mout at which any particular portion of theslurry is collected 1n the kiln.

Apart from the inherent tendency of the material to resist transport bythe gases the wetter it is there is an advantage in causing the zones tobe progressively wetter in a direc` ilarly dispersing it exerts aneffect in resist-l ing the transporting action of the gases, for thecoarser these are the. less readily do the gases carry them. Again(particles which are coarse enough to resist un uly easy transport outof the kiln can if Well filling a cross section of the kiln exert amarked gas-cleansing action on gases coming to the cross section andbearing relatively fine particles of material with them. These areadvantages which can be obtained by making in any suit*- able way theatomization less complete the nearer the kiln mouth that atomization iseffected and are results that to a considerable extent flow from themode of atomizat-ion where zones of atomization in the kiln are producedby spray nozzles or the like outside the kiln, for, the further a nozzleor the like has to project the material it is to atomize' the greaterthe head required usually and the finer as a rule will be atomization ofthe material at the region to which it is to be projected.

In atomizing or similarly dispersing slurry in a kiln, circumstances mayarise rendering it necessary temporarily to suspend the dispersing, forexample when it is desired to clean or repair a nozzle; and did thisinvolve f a cessation of cement making in the kiln it would be a graveinconvenience seeing that Kill till

into the kiln at some 30 to the vertical. This opening 31 is closed by acap, as indicated in Figure l, when the atomizing method of cementmaking is in operation.

In Figure 4 the kiln head is shown as converted into a reservoir forslurry over which the gases from the kiln are caused to pass in flowingdown between the rear wall 5 of the head and'thefront wall'35 ofthe-latter and up behind the wall 5 and over the wall 37 away to thechimney, this slurry (which is fed in through an inlet 33) being keptstirred by compressed air from pipes indicated at 39 and withdrawn froma well 41 outside the kiln head and into which well the slurry passesthrough an opening 43 below the levels of the liquid in the reservoirand well.

Where the slurry from the well 41 is used to feed the spraylng nozzlesyof this slurry obviously becomes advantageously concentrated (by actualevaporation of the water from it and also by cement material carried outof the kiln by the gases) before being passed to the kiln.

A pipe 45 is shown in Figure 4 dipping into the liquid in the well 43and this pipe leads to a pump 47 discharging through a pipe 49 into aslurry supply tank 51 into which the main supply of slurry is fedthrough the pipe 53 and from which tank the slurry received from thepipes 49 and 53 passes by a pipe 55 to a pump 57 and thence by a pipe 58and branch pipes 59 to the spray nozzles.

If weak slurry is used and it does not by the admixture with it ofdeposited matter and evaporation of its water reach a condition whichfits it for supply, if desired, to the kiln it may be used in the slurrymaking installation of the plant so that its contents of cementmaterials shall not be wasted. Such an exposure of the gases to slurryin passing from the kiln to the chimney will in most cases cleanse thesegases from cement dust better than the means ordinarily in use in cementplants. rllhe exposure of the gases leaving the kiln to the cleansingand cooling action ofslurry may be effected by exposing the gasesoutside the kiln to slurry in an atomizedor similarly dispersedcondition. While this may be done in a'specially provided gas coolingtower or the like to which the gases pass from the kiln head the smokechamber in the kiln head itselfmay be made use of by providing insteadof or in addition to a container for liquid as has been abovementioned', suitable slurry atomizing or like dispersing means such forexample as one or more slurry spraying nozzles directing a spray orsprays down the kiln head from, and it may be through, one or moreopenings in the kiln 'head at or near its top.

The slurry may either be passed through the gas contact space outsidethe kiln and forthwith utilized as desired or it may be continuouslwithdrawn from the said s ace and returne to it anew only a portion othepcirculating slurry being continuously or from t kiln and accordinglyit may be desirable after any such slurry is withdrawn from the devicein which it is ex osed to the gases from the kiln and prefera ly beforesuch withdrawn slurry passes to a slurry pump or the like supplying thespray nozzles or like device, to subject it to mixing or grinding andmixing treatment.

Instead of compressed air being used for agitating the slurry, paddlesor their equi-valent may be used in any desired combination and it mayin some cases be advantageous to arrange that the container for slurrywhich collects the material carried out of the kiln by the gases ispartly in the kiln head and partly outside the head to facilitateprovision of stirring and mixing devices.

Concentration of slurry by evaporation of Water from it outside the kilnby the heat of.

the gases from the kiln need not be a factor of any considerableeconomic moment if the dispersal of the slurry in the gases in the kilnis efficiently performed, fprl then the gases can be made to leave thekiln at a comparatively low temperature and it is contemplated that in acase such as described with reference to Figures 1 to 3 this temperatureneed not be more than some 150o C. or thereabouts.

lt will be understood that where according to the invention arrangementslare used whichA aim at the production by different atomizing or'likedevices of different zones of atomized slurry lengthwise of the kiln anynumber of such zones may be aimed at, be it two or any greater number.In most cases there will be a certain overlapping or merging of one zonein the adjacent one or the two adjacent ones so that no such precisedemarcation of the zones as has for illustrative purposes been assumedto exist in the foregoing discussion will in fact generally exist7 atall events where no attempt is made for any reason actually to havedefinite intervals in between the zones.

The length of the kiln which is to be more or less filled with thedispersed slurry is also variable within wide limits according tocircumstances. Ordinarily this will not be less than some 20 feet to 30feet as is indicated in Figure 1 and will generally be confined to somesuch length of the kiln. t

rll`he apparatus described and illustrated shows separate jets forprojecting the dispersed slurry into different regions spread lengthwiseof the kiln butit should be understood that any single nozzle orequivalent dethe kiln vice which projects two or more correctlyproportioned sprays to the aforesaid dierent regions eitherconcentrically or in any other manner may be used where desired inaddition to or instead of separate nozzles.

What I claim as my invention and desire to secure by Letters Pat-ent is:

l. A process ot' making cement by subjecting slurry to a heat-treatmentin an elongated eylindrieal heated kiln inclined slightly to thehorizontal, that comprises projecting from different slurry-supplyinglocations outside the kiln a slurry in a finely divided condition todifferent regions in and spaced lengthwise of the kiln and rotating theslightly inclined kiln to cause material thus vdelivered to it toprogress down it.

2. In a process of making cement in an inclined rotary kiln havin@ alseparate drying zone, and ealeining and tilinkerinv zones, the steps ofsupplying a plurality oindependently controlled streams of finelydivided atomized slurry flowing along converging axes to the interiorsurface of the said drying zone at different regions spaced lengthwiseof said zone, and passing hot gases of combustion in countercurrent tothe slurry flow.

3. In a process of making cement in an inclined rotary kiln having aseparate drying zone, and calcining and clinkcrinw zones, the steps ofsupplying-a plurality oiF independently controlled streams of finelyldivided atoluized slurry flowing along converging axes to the interiorsurface of the said drying zone, subjecting the independently controlledstreams of slurry to different pressures to deliver theslurry atydifferent regions spaced lengthwise of said drying zone, and passinghot' gases of combustion in countercurrent to the slurry flow.

In testimony whereof I affix my signature.

f THOMAS RIGBY.

